Field of the Invention
The invention relates to a method of fixing the conductors and coils of winding overhangs and of filling cavities in the winding overhangs of electrical machines by pulling in strings which comprise compressible rovings made up of fibers and surrounded by an elastic sheath which is permeable to impregnating resin, the spacing means being introduced into the winding overhangs with a thickness greater than the spacings to be filled and the strings being impregnated after being pulled in.
The invention furthermore relates to a string for carrying out the method.
Discussion of Background
In rotating electrical machines, in particular in fairly large motors and generators, the conductors and coils of exposed winding sections, referred to here collectively as winding overhangs, are spaced and mutually supported. In the method disclosed in German Patent Specification DE-PS 14 88 429 of fixing the conductors and coils of winding overhangs and of filling cavities in the winding overhangs of electrical machines, impregnatable strings are used. These strings have a core composed of fibers in the form of a compressible roving surrounded by an elastic sheath. The spacing means is introduced into the winding overhangs with a thickness which is larger than the spacings to be filled. In this method, the strings are impregnated only after they have been pulled in.
The conductors and coils in the winding overhang of such electrical machines are, without exception, provided with a corona shielding, the overhang corona shielding. If the strings are now pulled in in the state described, despite the elasticity inherent in the strings, regions may be produced in which the strings are not fully in contact with the conductors and coils. Although this does not result primarily in a mechanical weakening of the winding overhang composite, partial discharges which in time result in a local destruction of the organic insulating components may occur in these regions.